Mini SD is a disappearing format (likely very difficult to get cards in the near future) and is not supported by SDXC. Could one use micro SDXC with adapters?
Best would be a different (SDXC or micro SDXC ) memory card input for the next batch!

"Power*5.0V ± 5%, 0.5A"
I see recommendations using 3 (4.5V) or 6 (6V) battery supplies? These are more than 5% off 5V. What is the real Voltage limit?